14 BULLETIN" 78, U. S. DEPARTMENT OP AGRICULTURE. 



destroy large numbers of Cramhus laqueatellus at Haw Patch, Ind., 

 and C. II. Fernald observed barn swallows feeding on different species 

 of Cramhus in Maine. Meadowlarks frequent weedy fields which 

 harbor the larvae of Crambus, and as these birds are known to feed 

 on various species of cutworms, they doubtless feed also on the larvae 

 of the tobacco Crambus. 



REPRESSION. 



CULTURAL METHODS OF CONTROL. 



Injury from the tobacco Crambus occurs where crops susceptible 

 to injury are grown on weedy land. Tobacco or corn planted on land 

 which has been under clean cultivation the previous year and kept 

 free from weeds which live throughout the winter does not suffer 

 serious injury. The larvse can not live over winter in the soil from 

 the previous summer unless plants on which they are able to feed are 

 present. All field experiments and observations so far have shown 

 that the most effective means of control consist of freeing the land 

 from the weeds, such as buckhorn plantain, daisy, stickweed, etc., 

 which have been found to be the natural food plants of the larva?. 



There are many methods by which weeds may be eradicated or 

 controlled, but the most practical and effective is the systematic 

 rotation of crops. Sowing clean seed, preventing weeds from ripen- 

 ing seed, fall or winter plowing, the use of lime or of certain fertil- 

 izers, and doing away with wide fence rows are important preven- 

 tive measures. Mowing and burning over weedy fields destroys 

 many weed seeds and weeds which live over winter, and also destroys 

 many injurious insects. Burning during August or September has 

 been found to destroy the eggs and young larvae of the tobacco 

 Crambus, but as this method destroys humus, which is so badly 

 needed in most tobacco soils, it is in most instances not advisable. 



Many weeds are "soil indicators/' their presence showing that the 

 soil is lacking in fertility and in some instances pointing to a deficiency 

 of lime. 



CLEAN SEED. 



One of the main factors in the control of weeds is clean seed, and 

 the importance of procuring such seed can hardly be overestimated. 

 Many weed pests are introduced and disseminated in the seed of 

 various crops, such as grass and clover. As tobacco or corn must 

 frequently be grown on land which has previously been in these 

 crops, and as injury from the tobacco Crambus is apt to occur if the 

 meadows have been weedy, it is desirable, for this and other reasons, 

 to have the meadows as free from weeds as possible. 1 Owing to 



1 An analysis made by the Massachusetts Experiment Station shows that 1 ton of oxeye daisy (cured) 

 withdraws from the soil approximately 2.5 pounds of potash, 8.7 pounds of phosphoric acid, 22 pounds of 

 nitrogen, and 2G pounds of lime. To restore the stated amounts of the first three constituents to the soil 

 it would be necessary to apply about 50 pounds of muriate of potash, 65 pounds of superphosphate, and 

 140 pounds of nitrate of soda. (Farmers' Bui. 103, V. B. Dept. Agr.) 



